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<br />City of Fort Collins <br />December 4, 198D <br />Page 4 <br /> <br />Consideration of these factors has lead us to recommend a combination <br />of improvements for Mail Creek and McClellands Basins, consisting <br />of selected structural improvements, detention, and continued flood- <br />plain management with flood insurance. The recommended improvements <br />to Reaches 1 and 2 of Mail Creek are shown schematically on Drawing 1 <br />attached. Our recommendation is to improve the Palmer Drive Spill- <br />way, Reach lC, construct new street crossings and a trapezoidal <br />channel in Reach 2A, and two detention ponds in Reach 2B, possibly <br />combining a flow separation structure with the pond embankment at <br />the Pleasant Valley and Lake Canal. <br /> <br />Because of the significant storage capacity existing in the New <br />Mercer Canal, the improvements recommended in Reaches 3, 4, and 5 <br />are considered separately from Mail Creek. These recommendations, <br />shown on Drawing 2, are to improve the spillway at the Larkborough <br />detention pond and to provide a multi-use detention facility at the <br />head of the 24-inch RCP storm sewer in Reach 4A. This facility is <br />recommended despite the B/C ratio of 0.8 because of the possibility <br />of reducing some construction costs if a multi-use facility is <br />designed. In Reach 4B, continued floodplain management and flood <br />insurance for the church, and continued floodplain management in <br />Reach 5 are recommended. <br /> <br />In the McClellands Basin, development has taken place mostly north <br />of Harmony Road and sound storm drainage practices have been observed. <br />In the lower reaches, flood damages are concentrated at Timberline <br />Road and the Union Pacific Railroad. Our recommendations for <br />McClellands are simply to provide improved culverts at these locations <br />and to continue the program of floodplain management. These are <br />illustrated schematically on Drawing 3. The improved culvert at the <br />railroad is particularly important due to the high probability of <br />an embankment failure during even a minor (lO-year) event. <br /> <br />Finally, a summary of the benefits and costs for these recommendations <br />are listed in the last table. For Mail Creek and McClellands, the <br />combined estimated construction is $805,210. We have broken these <br />costs down on a per acre basis as noted in the table, as you requested. <br /> <br />We trust this information will provide the basis for a decision for <br />a flood control plan in these basins. We are, of course, available <br />to answer any questions or to supply additional data should you <br />requi re it. <br /> <br />Respectfully submitted, <br />A/~LTIN OMPANY <br /> <br /> <br />Donald M. Pa ons, <br />Vice preside t <br /> <br /> <br />a~::(*o <br /> <br />Design Engineer <br /> <br />P.E. <br />